scholarly journals Ultracompact H ii regions with extended emission: the complete view

2019 ◽  
Vol 492 (1) ◽  
pp. 895-914 ◽  
Author(s):  
Eduardo de la Fuente ◽  
Alicia Porras ◽  
Miguel A Trinidad ◽  
Stanley E Kurtz ◽  
Simon N Kemp ◽  
...  
Keyword(s):  
Morphological Study ◽  
Galactic Plane ◽  
Radio Continuum ◽  
H Ii Regions ◽  
Direct Connection ◽  
Infrared Excess ◽  
Very Large Array ◽  
Bubble Structure ◽  
Colour Composite ◽  
Extended Emission

ABSTRACT In this paper, we present the results of a morphological study performed on a sample of 28 ultracompact H ii (UC H ii) regions located near extended free–free emission, using radio continuum (RC) observations at 3.6 cm with the C and D Very Large Array (VLA) configurations, with the aim of determining a direct connection between them. By using previously published observations in B and D VLA configurations, we compiled a final catalogue of 21 UC H ii regions directly connected with the surrounding extended emission (EE). The observed morphology of most of the UC H ii regions in RC emission is irregular (single- or multipeaked sources) and resembles a classical bubble structure in the Galactic plane with well-defined cometary arcs. RC images superimposed on colour composite Spitzer images reinforce the assignations of direct connection by the spatial coincidence between the UC components and regions of saturated 24 μm emission. We also find that the presence of EE may be crucial to understand the observed infrared excess because an underestimation of ionizing Lyman photons was considered in previous works (e.g. Wood & Churchwell; Kurtz, Churchwell & Wood).

scholarly journals Ultracompact H ii regions with extended emission: the case of G43.89–0.78 and its molecular environment

2020 ◽  
Vol 497 (4) ◽  
pp. 4436-4447
Author(s):  
Eduardo de la Fuente ◽  
Daniel Tafoya ◽  
Miguel A Trinidad ◽  
Alicia Porras ◽  
Alberto Nigoche-Netro ◽  
...  
Keyword(s):  
Operational Definition ◽  
Radio Continuum ◽  
Physical Parameters ◽  
Kinetic Temperature ◽  
H Ii Regions ◽  
Owens Valley ◽  
Very Large Array ◽  
Compact Component ◽  
H Ii Region ◽  
Extended Emission

ABSTRACT The Karl Jansky Very Large Array (VLA), Owens Valley Radio Observatory (OVRO), Atacama Large Millimetric Array (ALMA), and the infrared Spitzer observatories are powerful facilities to study massive star formation regions and related objects such as ultra-compact (UC) H ii regions, molecular clumps, and cores. We used these telescopes to study the UC H ii region G43.89–0.78. The morphological study at arcminute scales using NVSS and Spitzer data shows that this region is similar to those observed in the bubble-like structures revealed by Spitzer observations. With this result, and including a physical characterization based on 3.6 cm data, we suggest G43.89–0.78 be classified as an UC H ii region with Extended Emission because it meets the operational definition given in this paper comparing radio continuum data at 3.6 and 20 cm. For the ultra-compact component, we use VLA data to obtain physical parameters at 3.6 cm confirming this region as an UC H ii region. Using ALMA observations, we detect the presence of a dense (2.6 × 107 cm−3) and small (∼ 2.0 arcsec; 0.08 pc) molecular clump with a mass of 220 M⊙ and average kinetic temperature of 21 K, located near to the UC H ii region. In this clump, catalogued as G43.890–0.784, water masers also exist, possibly tracing a bipolar outflow. We discover in this vicinity two additional clumps which we label as G43.899–0.786 (Td = 50 K; M  = 11 M⊙) and G43.888–0.787 (Td = 50 K; M  = 15 M⊙).

scholarly journals CO line and radio continuum study of elephant trunks: the Pillars of Creation in M16

2020 ◽  
Vol 492 (4) ◽  
pp. 5966-5979 ◽  
Author(s):  
Yoshiaki Sofue
Keyword(s):  
Surface Brightness ◽  
Galactic Plane ◽  
Brightness Distribution ◽  
Radio Continuum ◽  
Very Large Array ◽  
Heating Source ◽  
Velocity Gradients ◽  
Magnetic Oscillation ◽  
H Ii Region ◽  
Line Survey

ABSTRACT Molecular line and radio continuum properties of the elephant trunks (ET, Pillars of Creation) in M16 are investigated by analysing 12CO(J = 1−0) , 13CO(J = 1−0) and C18O(J = 1−0) line survey data from the Nobeyama 45-m telescope and the Galactic plane radio survey at 20 and 90 cm with the Very Large Array. The head clump of Pillar West I is found to be the brightest radio source in M16, showing a thermal spectrum and the properties of a compact H ii region, with the nearest O5 star in NGC 6611 being the heating source. The radio pillars have a cometary structure concave to the molecular trunk head, and the surface brightness distribution obeys a simple illumination law from a remote excitation source. The molecular density in the pillar head is estimated to be several 104 H2 cm−3 and the molecular mass is $\sim 13\!-\!40 \, \mathrm{M}_\odot$. CO-line kinematics reveals random rotation of the clumps in the pillar tail at ∼1–2 km s−1, comparable with the velocity dispersion and estimated Alfvén velocity. It is suggested that the random directions of the velocity gradients would manifest as torsional magnetic oscillation of the clumps around the pillar axis.

The diagnostic power of radio spectra from star-forming galaxies

2019 ◽  
Vol 15 (S341) ◽  
pp. 177-186
Author(s):  
Eric J. Murphy
Keyword(s):  
Star Formation ◽  
Dust Emission ◽  
Cosmic Ray ◽  
Microwave Emission ◽  
Radio Continuum ◽  
Continuum Emission ◽  
H Ii Regions ◽  
Synchrotron Emission ◽  
Very Large Array ◽  
Star Forming

AbstractRadio continuum emission from galaxies is powered by a combination of distinct physical processes, each providing unique diagnostic information. Over frequencies spanning ∼ 1–120 GHz, radio spectra of star-forming galaxies are primarily comprised of: (1) non-thermal synchrotron emission powered by accelerated cosmic-ray electrons/positrons; (2) free-free emission from young massive star-forming (H ii) regions; (3) anomalous microwave emission, which is a dominant, but completely unconstrained, foreground in cosmic microwave background experiments; and (4) cold, thermal dust emission that accounts for most of the dust and total mass content in the interstellar medium in galaxies. In this proceeding, we discuss these key energetic processes that contribute to the radio emission from star-forming galaxies, with an emphasis on frequencies ≳30 GHz, where current investigations of star formation within nearby galaxies show that the free-free emission begins to dominate over non-thermal synchrotron emission. We also discuss how planned radio facilities that will access these frequencies, such as a next-generation Very Large Array (ngVLA), will be transformative to our understanding of the star formation process in galaxies.

scholarly journals New insights in giant molecular cloud hosting the S147/S153 complex: signatures of interacting clouds

2020 ◽  
Author(s):  
Jayakumar Sushama Dhanya ◽  
Lokesh Kumar Dewangan ◽  
Devendra Kumar Ojha ◽  
Subhayan Mandal
Keyword(s):  
Molecular Cloud ◽  
Near Infrared ◽  
Galactic Plane ◽  
Line Of Sight ◽  
H Ii Regions ◽  
Infrared Excess ◽  
Ob Stars ◽  
Giant Molecular Cloud ◽  
Multi Wavelength ◽  
Perseus Arm

Abstract In order to understand the formation of massive OB stars, we report a multi-wavelength observational study of a giant molecular cloud hosting the S147/S153 complex (size ${\sim}90\:\:\mbox{pc} \times 50\:$pc). The selected complex is located in the Perseus arm, and contains at least five H ii regions (S147, S148, S149, S152, and S153) powered by massive OB stars with dynamical ages ${\sim}0.2$–$0.6\:$Myr. The Canadian Galactic Plane Survey $^{12}$CO line data (beam size ${\sim}{100{^{\prime \prime}_{.}}4}$) trace the complex in a velocity range of [$-59$, $-43]\:$km$\:$s$^{-1}$, and also reveal the presence of two molecular cloud components around $-54$ and $-49\:$km$\:$s$^{-1}$ in the direction of the complex. Signatures of the interaction/collision between these extended cloud components are investigated through their spatial and velocity connections. These outcomes suggest the collision of these molecular cloud components about $1.6\:$Myr ago. Based on the observed overlapping zones of the two clouds, the collision axis appears to be parallel to the line-of-sight. Deep near-infrared photometric analysis of point-like sources shows the distribution of infrared-excess sources in the direction of the overlapping zones of the molecular cloud components, where all the H ii regions are also spatially located. All elements put together, the birth of massive OB stars and embedded infrared-excess sources seems to be triggered by two colliding molecular clouds in the selected site. High-resolution observations of the dense gas tracer will be required to further confirm the proposed scenario.

scholarly journals Gas kinematics and star formation in the filamentary molecular cloud G47.06+0.26

2018 ◽  
Vol 609 ◽  
pp. A43 ◽  
Author(s):  
Jin-Long Xu ◽  
Ye Xu ◽  
Chuan-Peng Zhang ◽  
Xiao-Lan Liu ◽  
Naiping Yu ◽  
...  
Keyword(s):  
Star Formation ◽  
Galactic Plane ◽  
Mass Density ◽  
Radio Continuum ◽  
Young Stellar Objects ◽  
H Ii Regions ◽  
Filamentary Structure ◽  
Gas Kinematics ◽  
Mean Width ◽  
The Galaxy

Aims. We performed a multi-wavelength study toward the filamentary cloud G47.06+0.26 to investigate the gas kinematics and star formation. Methods. We present the 12CO (J = 1−0), 13CO (J = 1−0) and C18O (J = 1−0) observations of G47.06+0.26 obtained with the Purple Mountain Observation (PMO) 13.7 m radio telescope to investigate the detailed kinematics of the filament. Radio continuum and infrared archival data were obtained from the NRAO VLA Sky Survey (NVSS), the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL), the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) survey, and the Multi-band Imaging Photometer Survey of the Galaxy (MIPSGAL). To trace massive clumps and extract young stellar objects in G47.06+0.26, we used the BGPS catalog v2.0 and the GLIMPSE I catalog, respectively. Results. The 12CO (J = 1−0) and 13CO (J = 1−0) emission of G47.06+0.26 appear to show a filamentary structure. The filament extends about 45′ (58.1 pc) along the east-west direction. The mean width is about 6.8 pc, as traced by the 13CO (J = 1−0) emission. G47.06+0.26 has a linear mass density of ~361.5 M⊙pc-1. The external pressure (due to neighboring bubbles and H II regions) may help preventing the filament from dispersing under the effects of turbulence. From the velocity-field map, we discern a velocity gradient perpendicular to G47.06+0.26. From the Bolocam Galactic Plane Survey (BGPS) catalog, we found nine BGPS sources in G47.06+0.26, that appear to these sources have sufficient mass to form massive stars. We obtained that the clump formation efficiency (CFE) is ~18% in the filament. Four infrared bubbles were found to be located in, and adjacent to, G47.06+0.26. Particularly, infrared bubble N98 shows a cometary structure. CO molecular gas adjacent to N98 also shows a very intense emission. H II regions associated with infrared bubbles can inject the energy to surrounding gas. We calculated the kinetic energy, ionization energy, and thermal energy of two H II regions in G47.06+0.26. From the GLIMPSE I catalog, we selected some Class I sources with an age of ~105 yr, which are clustered along the filament. The feedback from the H II regions may cause the formation of a new generation of stars in filament G47.06+0.26.

scholarly journals FOREST Unbiased Galactic Plane Imaging Survey with the Nobeyama 45 m telescope (FUGIN). IV. Galactic shock wave and molecular bow shock in the 4 kpc arm of the Galaxy

2018 ◽  
Vol 71 (Supplement_1) ◽  
Author(s):  
Yoshiaki Sofue ◽  
Mikito Kohno ◽  
Kazufumi Torii ◽  
Tomofumi Umemoto ◽  
Nario Kuno ◽  
...  
Keyword(s):  
Shock Wave ◽  
Shock Front ◽  
Galactic Plane ◽  
Tangential Direction ◽  
Bow Shock ◽  
Radio Continuum ◽  
Dimensional Structure ◽  
H Ii Regions ◽  
Ionized Gas ◽  
The Galaxy

Abstract The FUGIN CO survey revealed the three-dimensional structure of a galactic shock wave in the tangential direction of the 4 kpc molecular arm. The shock front is located at G30.5+00.0 + 95 km s−1 on the upstream (lower longitude) side of the star-forming complex W 43 (G30.8−0.03), and comprises a molecular bow shock (MBS) concave to W 43, exhibiting an arc-shaped molecular ridge perpendicular to the galactic plane with width ∼0${^{\circ}_{.}}$1(10 pc) and vertical length ∼1° (100 pc). The MBS is coincident with the radio continuum bow of thermal origin, indicating association of ionized gas and similarity to a cometary bright-rimmed cloud. The upstream edge of the bow is sharp, with a growth width of ∼0.5 pc indicative of the shock front property. The velocity width is ∼10 km s−1, and the center velocity decreases by ∼15 km s−1 from the bottom to the top of the bow. The total mass of molecular gas in the MBS is estimated to be ∼1.2 × 106 M⊙, and ionized gas ∼2 × 104 M⊙. The vertical disk thickness has a step-like increase at the MBS by ∼2 times from lower to upper longitudes, which indicates hydraulic jump in the gaseous disk. We argue that the MBS was formed by the galactic shock compression of an accelerated flow in the spiral-arm potential encountering the W 43 molecular complex. A bow-shock theory can reproduce the bow morphology well. We argue that molecular bows are common in galactic shock waves, not only in the Galaxy but also in galaxies, where MBSs are associated with giant cometary H ii regions. We also analyzed the H i data in the same region to obtain a map of H i optical depth and molecular fraction. We found firm evidence of the H i to H2 transition in the galactic shock as revealed by a sharp molecular front at the MBS front.

scholarly journals Discovery of a New Population of Galactic H ii Regions with Ionized Gas Velocity Gradients

2021 ◽  
Vol 921 (2) ◽  
pp. 176
Author(s):  
Dana S. Balser ◽  
Trey V. Wenger ◽  
L. D. Anderson ◽  
W. P. Armentrout ◽  
T. M. Bania ◽  
...  
Keyword(s):  
Solid Body ◽  
Galactic Plane ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
H Ii Regions ◽  
Very Large Array ◽  
Bipolar Outflow ◽  
Velocity Gradients ◽  
Independent Observations ◽  
Many Sources

Abstract We investigate the kinematic properties of Galactic H ii regions using radio recombination line (RRL) emission detected by the Australia Telescope Compact Array at 4–10 GHz and the Jansky Very Large Array at 8–10 GHz. Our H ii region sample consists of 425 independent observations of 374 nebulae that are relatively well isolated from other, potentially confusing sources and have a single RRL component with a high signal-to-noise ratio. We perform Gaussian fits to the RRL emission in position-position–velocity data cubes and discover velocity gradients in 178 (42%) of the nebulae with magnitudes between 5 and 200 m s − 1 arcsec − 1 . About 15% of the sources also have an RRL width spatial distribution that peaks toward the center of the nebula. The velocity gradient position angles appear to be random on the sky with no favored orientation with respect to the Galactic plane. We craft H ii region simulations that include bipolar outflows or solid body rotational motions to explain the observed velocity gradients. The simulations favor solid body rotation since, unlike the bipolar outflow kinematic models, they are able to produce both the large, >40 m s − 1 arcsec − 1 , velocity gradients and also the RRL width structure that we observe in some sources. The bipolar outflow model, however, cannot be ruled out as a possible explanation for the observed velocity gradients for many sources in our sample. We nevertheless suggest that most H ii region complexes are rotating and may have inherited angular momentum from their parent molecular clouds.

Stellar feedback in dwarf irregular galaxies with radio continuum observations

2018 ◽  
Vol 14 (S344) ◽  
pp. 255-258
Author(s):  
Volker Heesen ◽  
Aritra Basu ◽  
Elias Brinks ◽  
George Heald ◽  
Andrew Fletcher ◽  
...  
Keyword(s):  
Star Formation ◽  
Low Frequency ◽  
Cosmic Ray ◽  
Radio Continuum ◽  
Very Large Array ◽  
Radio Halo ◽  
Spatially Resolved ◽  
Ic 10 ◽  
Irregular Galaxies ◽  
Dwarf Irregular Galaxies

AbstractLow-mass dwarf irregular galaxies are subject to outflows, in which cosmic rays may play a very important role; they can be traced via their electron component, the cosmic ray electrons (CRe), in the radio continuum as non-thermal synchrotron emission. With the advent of sensitive low-frequency observations, such as with the Low-Frequency Array (LOFAR), we can trace CRe far away from star formation sites. Together with GHz-observations, such as with the Very Large Array (VLA), we can study spatially resolved radio continuum spectra at matched angular resolution and sensitivity. Here, we present results from our 6-GHz VLA survey of 40 nearby dwarf galaxies and our LOFAR study of the nearby starburst dwarf irregular galaxy IC 10. We explore the relation of RC emission with star formation tracers and study in IC 10 the nature of a low-frequency radio halo, which we find to be the result of a galactic wind.

Bipolar outflow of gas in the spiral galaxy NGC 3079

1986 ◽  
Vol 64 (4) ◽  
pp. 531-535 ◽  
Author(s):  
Nebojsa Duric ◽  
E. R. Seaquist
Keyword(s):  
Spectral Index ◽  
Spiral Galaxy ◽  
Central Region ◽  
Qualitative Description ◽  
Radio Continuum ◽  
Large Array ◽  
Very Large Array ◽  
Bipolar Outflow ◽  
The Galaxy

Very large array, radio-continuum observations of the edge-on spiral galaxy NGC 3079 are presented. The observations reveal that the nucleus has windlike properties and that the central region of the galaxy exhibits an unusual figure-eight morphology that shows evidence of severe depolarization and a flattening spectral index away from the nucleus. A qualitative description of a model is presented to account for the observed radio properties. It is shown that a wind-driven shock propagating away from the nucleus and focused by the ambient disk gas can give rise to the observed morphology.

scholarly journals Low frequency (74 MHz) radio continuum observations of the inner 13° × 7° of the Galactic center

2013 ◽  
Vol 9 (S303) ◽  
pp. 464-466
Author(s):  
M. Rickert ◽  
F. Yusef-Zadeh ◽  
C. Brogan
Keyword(s):  
High Resolution ◽  
Molecular Cloud ◽  
Supernova Remnant ◽  
Galactic Center ◽  
Low Frequency ◽  
Radio Continuum ◽  
Large Array ◽  
Very Large Array ◽  
Image Displays ◽  
Western Side

AbstractWe analyze a high resolution (114″ × 60″) 74 MHz image of the Galactic center taken with the Very Large Array (VLA). We have identified several absorption and emission features in this region, and we discuss preliminary results of two Galactic center sources: the Sgr D complex (G1.1–0.1) and the Galactic center lobe (GCL).The 74 MHz image displays the thermal and nonthermal components of Sgr D and we argue the Sgr D supernova remnant (SNR) is consistent with an interaction with a nearby molecular cloud and the location of the Sgr D Hii region on the near side of the Galactic center. The image also suggests that the emission from the eastern side of the GCL contains a mixture of both thermal and nonthermal sources, whereas the western side is primarily thermal.

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